1. Technical Field
The disclosure relates to transducer arrays for producing sound, and more particularly to a high power sound source for use in liquids.
2. Description of the Problem
Sound is a disturbance in the physical properties of an elastic material/medium that propagates through the material. The disturbed physical properties can be the alternation in pressure, the displacement of particles or a change in the density of the elastic material/medium. An acoustic pressure wave will have alternating zones of high and low pressure, which can be referred to as the compression and rarefaction waves. An acoustic pressure wave propagating through a liquid (and possibly through a solid) medium can produce phase changes and otherwise affect physical properties of the liquid medium due to changing pressure. Pressure drops in a liquid medium can result in the liquid medium itself turning to vapor, gasses dissolved in the liquid leaving solution, or both. In other words, bubbles can be produced. These bubbles are termed acoustic cavitation bubbles. Usually acoustic cavitation bubbles rapidly collapse, which in turn can produce intense shock waves.
Whether acoustic cavitation bubbles are a problem in a given situation depends upon the system. For example, in systems where the pressure variation is highest at the surfaces of the transducers acoustic cavitation bubbles occur along these surfaces and their occurrence decreases rapidly with increasing distance from the surface of the transducer. In such systems the transducer surfaces are vulnerable to damage from acoustic cavitation.
The acoustic cavitation phenomenon can also limit the amount of power that can be transferred from the transducer element(s) to the propagating medium and distort the resulting signal. A cavitation resistant array was proposed in U.S. Pat. No. 6,050,361 in which interstices of the sonar array between transducers was designed to match the specific acoustic impedance of water.